Gas-fired infrared burners and heaters



July 11, 1967 K. E. BAUER 3,330,267

GAS-FIRED INFRARED BURNERS AND HEATERS Filed Sept. 3, 1963 '7 Sheets-Sheet 1 INVENTOR Konrad E. Bauer BY J WW ATTORNEY5 July 11, 1967 K. E. BAUER 3,330,267

cmswnwo INFRARED BURNERS AND HEATERS Filed Sept. 5, 1963 7 Sheets-Sheet 2 INVENTOR Konrad E.Buuer ATTORNElQg July 11, 1967 K. E. BAUER 3,330,267

GAS-FIRED INFRARED BURNERS AND HEATERS Filed Sept. 5, 1963 7 Sheets-Sheet 3 INVENTOR Konrad E. Bauer 57 BY Q%@/% ATTORNEYS July 11, 1967 K. E. BAUER 3,330,267 GAS-FIRED INFRARED BURNERS AND HEATERS Filed Sept. 1963 7 Sheets-Sheet 4 INVENTOR Konrad E. Bauer ATTORNEYS July 11, 1967 BAUER 3,330,267

GA$-FIRED INFRARED BURNERS AND HEATERS Filed Sept. 5, 1963 7 Sheets-Sheet 5 INVENTOR Konrad E.Bouer ATTORNEYS K. E. BAUER GAS-FIRED INFRARED BURNERS AND HEATERS July 11, 1967 7 SheetsSheet 6 Filed Sept.

% WE y ATTORNEYS y 1967 K. E. BAUER 3,330,267

GAS-FIRED INFRARED BURNER-S AND HEATERS Filed Sept. 5, 1963 '7 Sheets-Sheet '7 INVENTOR Konrad E. Bauer BY /W %4 ATTORNEYZ' United States Patent 3,330,267 GAS-FIRED INFRARED BURNERS AND HEATERS Konrad E. Bauer, Mentor, Ohio, assignor to Hupp Corporation, Cleveland, Ohio, a corporation of Virginia Filed Sept. 3, 1963, Ser. No. 306,658 14 Claims. (Cl. 126-92) This invention relates to heating equipment, and more specifically, to novel gas-fired infrared burners and to novel heaters in which the burners are incorporated.

While our novel burners are described as gas-fired, it should be understood that the term gas includes combustible gases which are stored under pressure as liquids and combustible liquids which can be vaporized for combustion in gaseous form.

Application Ser. No. 243,916, filed Dec. 11, 1962, now Patent No. 3,245,458, by Malcolm W. Patrick and myself, discloses infrared generators in which a mixture of gas and enough air for its complete combustion flows through a thin perforated plate and burns on the plates exterior surface, heating it to incandescence. The radiant face thus provided my be a fiat sheet, a cylinder, a cone or other surface and i generally formed of heat-resisting metal. The plate is heated throughout its thickness to an incandescent temperature far in excess of the ignition temperature of the mixture in contradistinction to prior art devices wherein the orifice plate was maintained at a sufficiently low temperature to keep the surface in contact with the unignited mixture at a temperature below the mixtures ignition temperature. A formula is set forth in application Ser. No. 243,916 by which the size and spacing of the perforations necessary to prevent flashback for specific design parameters and specific types of fuel gases can be determined.

Burners of the type disclosed in the copending application are often provided with a reradiator spaced from the radiant face. The reradiator is heated by the burning gases and by radiation from the primary radiant face and materially increases the amount of radiation emitted by burning a given amount of fuel. The reradiator is generally a screen or sheet with comparatively large perforations and an open area sufficiently large to allow free flow of the products of combustion.

The present invention relates to burners of the type just described. Among the objects of this invention are the provision of novel, improved infrared generators characterized by:

(l) A very high heating capacity size ratio;

(2) A low manufacturing cost per unit of capacity;

(3) A high radiant efliciency;

(4) Extremely high suitability for use outdoors or where windy conditions exist;

(5) Rapid attainment of operating temperatures so that heat is, for practical purposes, instantly available when the burner is turned on;

(6) High resistance to warping and other adverse temperature change induced deterioration;

(7) Easy replacement of the radiant element, permitting higher operating temperatures and/or use of less expensive though less durable materials as the radiant element can be economically replaced if it burns out;

(8) Adaptability of the generator to many uses such as in outdoor and indoor radiant heating, in heat exchangers for winter air conditioning, in water heaters, in

3,330,267 Patented July 11, 1967 "ice processing applications of many kinds, in food preparation, and in heating units for absorption refrigeration and thermoelectric generators.

These goals are attained by incorporating novel im proved reradiators disclosed herein into burners of the type disclosed in application Ser. No. 243,916. The reradiators of the present invention enclose the primary radiant face and preferably have a surface area several times as large as the area of the primary radiant face. In addition, our improved reradiators have many small holes or perforations, the total area of which exceeds the total area of the larger holes in an equally sized screen type reradiator as described in the copending application.

The present invention provides a more uniformly heated reradiator of greater surface area and provides materially better protection for the flame burning on the exterior surface of radiant face.

To ensure that combustion Will always be initiated on the primary radiant face, even though the burner is lighted from outside the reradiator, at least one larger hole is provided in the reradiator through which the flame may flash back and burn on the inner primary radiant face without igniting the mixture behind the radiant face.

In the improved burners of the present invention most of the radiation is emitted from the reradiator which is heated by radiation from the primary face and by combustion taking place on the primary face. The burner is always supplied with a mixture containing at least 100% primary air.

One typical burner according to the present invention has a primary radiant member of IncOnel (or other metal of equal heat resistance) 0.012 inch thick shaped as a truncated cone and has an area of 10 square inches. It is perforated with 9,520 0.020" diameter perforations totalling three square inches in area. The reradiator is a cylinder with an inverted conical head. The cylinder and head have a total area of square inches and are perforated with 23,170 0.033 diameter holes and six A diameter holes. The aggregate area of the holes in the reradiator is 20 square inches.

In this exemplary burner the total area of the reradiating surface is seven times the area of the primary radiant surface, and the area of the openings in the reradiator is nearly seven times the area of the perforations in the primary radiant member.

This burner is designed to burn propane gas and its C factor, calculated according to the formula set forth in our copending application, is 0.00006, well below the value of 0.0005 which is critical in the co-pending burner and above which flashback may occur.

The small holes in the reradiating surface prevent flame disturbance by gusts of Wind. The large area of incandescent metal in the reradiator, concentrated into a cylindrical member only 3 /2" in diameter and 5" long, provides a very compact and highly efiicient burner which can burn gas at a rate of up to 45,000 b.t.u. per hour and can convert a very large percentage of the heat of combustion to radiant energy.

From the foregoing, it will be apparent that it is a further object of the present invention to improve infrared generators of the type set forth in our prior applica tion by providing them with reradiators having: (a) a surface area at least twice as great as the area of the primary radiant face; (b) numerous small openings with an aggregate area at least twice the aggregate area of the over its entire area, thereby preventing excessively hot spots and cool spots which reduce the efficiency of the burner, and shorten the life of the material.

Another specific object of this invention is the provision of burners in accordance with the foregoing objects in which the primary radiant member and the reradiator are combined into an independent unit attached to its supporting structures by a quick-disconnect type device so that the unit can be readily removed and replaced.

It is another specific object of the present invention to provide improved post-mounted outdoor heaters having burners with the advantages described above and novel components for concentrating or diffusing the emitted radiant energy and projecting it in any desired direction. t It is another object of the present invention to provide novel outdoor heaters incorporating the improved burners of the present invention which are constructed to protect the heater controls against the effects of adverse weather conditions.

I Another object of this invention is to provide novel burner venturi shields which will admit combustion air, but will protect the air inlet from the disturbing effects of wind, rain and snow, permitting burner operation in inclement weather.

A further object of this invention is the provision of gas-fired infrared generators and heating units which are characterized by compact construction, structural simplicity, low manufacturing cost, strength and ease of assembly, attractive appearance, ease of use, and long, trouble-free life.

These and other advantages and objects of the present invention will become more fully apparent by reference to the appended claims and as the following detailed description of a preferred embodiment proceeds in reference to the accompanying drawings wherein:

FIGURE 1 is a side elevation of a post-mounted heating unit constructed in accordance with the present invention;

FIGURE 2 is a rear view of the heating unit looking substantially in the direction of arrows 2-2 of FIGURE 1;

FIGURE 3 is a fragmentary side elevation of the heating unit, showing the shield covering the venturi mixer and fuel inlet;

FIGURE 4 is a horizontal sectional view through the post and control cas ing with the valve and piping omitted,

. and'is taken substantially along line 4-4 of FIGURE 1;

FIGURE 5 is a vertical section through the control casing, showing the casing cover closed, and is taken substantially along line 55 of FIGURE 4;

FIGURE 6 is a plan view of the heating unit with certain parts broken away to show its internal construction, and is taken substantially along line 6-6' of FIG- URE 1; V 7

FIGURE 7,is a longitudinal section through the heating units radiant member, taken substantially along line 77 of FIGURES;

FIGURE 8 is a transverse section through the heating unit burner, taken substantially along line 8-8 of FIG- URE 7;

FIGURE 9 is a fragmentary sectional view of the quick disconnect type connector employed to attach the radiant member to the venturi and is taken substantially along line 9-9 of FIGURE 8;

FIGURE 10 is a side view of the burner venturi, looking in the direction of arrows 1010 of FIGURE 6;

FIGURE 11 is an end view of the venturi, looking in the direction of arrows 1111 of FIGURE 10;

FIGURE 12 is a front view of a wire guard located at the open end of the heating unit reflector;

FIGURE 13 is a sectional view of the wire guard shown in FIGURE 12, looking in the direction of arrows 13-13 of FIGURE 12;

FIGURE 14 is a plan view of a spacer incorporated in the connector of FIGURES;

FIGURE 15 is a plan view of a locking plate incorporated in the connector of FIGURE 8;

FIGURE 16 is a plan view of a'ring at the bottom of the burner which forms part of the connector of FIG- URE 8;

FIGURE 17 is a perspectiveview of a swivel plate employed in the heating unit of FIGURE 1 and the trunnions by which the heating unit is pivotally mounted on the swivel plate;

FIGURE 18 is a fragmentary elevation of 'a modified reradiator constructed inaccordance with the principles of the present invention;

FIGURE 19 is a sectional view of the reradiator-of FIGURE 18, looking in the direction of arrows 19-19 of the latter figure;

FIGURE 20 is a fragmentary elevation of a third form of reradiator constructed in accordance with the principles of the present invention; 7

FIGURE 21 is a sectional view of the reradiator of FIGURE 20, looking in the direction of arrows 21-21 of FIGURE 20;

FIGURE 22 is a fragmentary longitudinal section through the primary radiant member and reradiator of a 'modified burner constructed in accordance with'the principles of the present invention, taken substantially along line 22-22 of FIGURE 23;

FIGURE 23 is a section through the modified burner of FIGURE 22, taken substantially along line 23-23 of that figure; 7

FIGURE 24 is a perspective view of a bafile employed in the modified burner of FIGURES 22 and 23;

FIGURE 25 is an elevation (partly in section) of still another form of radiant member'and a modified burner;

FIGURE 26 is a partly schematicillustration of an electric ignition and safety control system which can be incorporated into the heating unit of FIGURE 1'; and

FIGURE 27 is a schematic view of another application for burners of the type shown in FIGURES 7 and 8.

Referring now to the drawings, FIGURE 1 shows a radiant heating unit 116 of the present invention supthereof to a valve 126 located in a post mounted control casing 128. From the valve, the gas passes through a pipe 130, a flexible conduit 132 (which may be a hose), and an elbow 134 to heating unit 116.

As shown in FIGURE 6, elbow 134 is attached to a 7 gas inlet fitting 136 by a connector 138. Fitting'136 is attached to heating unit 116 by a lock nut 140. An outlet spud142 having an orifice 144 is screwed into fitting and meters the gas flowing through supply pipe 124 into 7 heating unit 116. Gas leaving orifice 144 flows into the bell 146 of burner venturi 148, entraining suflicient air to completely burn all of the gas. The gas and air are mixed together as they flow through venturi 148. 7

Turning next to FIGURE 7, the mixture of gas and air passes from venturi 148 to the interior of a radiant unit 150 comprised of a base ring 152, a sleeve 154, a radiant support ring156, a primary radiant member 158, a baflie 160, a reradiator sleeve 162, and a conical reradiator cover 164, all attached together by overlapping and spotwelding the joints between these components. .The enclosure 'bounded by base ring 152, sleeve 154, ring 156, I

primary radiant wall 158, and baffle 160 forms a distribution chamber 166 for the gas-air mixture.

Components 152, 154, 156, and 160 are preferably made of a heat resistant metal such as stainless steel. Primary radiant member 158 is made of Inconel or other material suitable for use at temperatures between 1200 and 2000 F. and is perforated with small holes 168. Radiant member 158 is 0.012" thick and, for use with propane gas, has 952 0.020 diameter holes per square inch of surface area. While this same radiant member can also be used with natural gas supplied at a suitable input rate and pressure best results with natural gas are ob tained by utilizing a radiant member with 233 0.040" diameter holes per square inch'of surface area. Various combinations of hole sizes and spacings and various plate thicknesses may be employed in the primary radiant member, as long as the C number as defined in application Ser. No. 243,916 is below 0.0005. The radiant member 153 in the burner of FIGURE 7 has a C value of 0.00006 when used with propane; the radiant member discussed above as best suited for natural gas has a C value of 0.0001 when 1311111111" this fuel.

Radiant member 153, shown as a truncated 45 degree cone, may have some other revolved shape such as hemispherical or may be a flat disc. The illustrated conical configuration is particularly advantageous, however, since it provides strength, rigidity, freedom from warping, is easily fabricated, and has a greater area than a flat disc of the same diameter. While materials other than perforated metal, such as ceramic plates or Wire screens, can be used, perforated metal has been found to be the most satisfactory and economical.

The gas-air mixture passes through the perforations in radiant member 158 and burns adjacent the surface of the radiant member remote from chamber 166 at 170, heating radiant member 158 throughout its thickness to temperatures above the ignition temperature of the mixture, at least a portion of the wall being heated to incandescence. Baflie 160 and the conical shape of radiant member 158 contribute to the production of a stable uniform flame at 170 and to uniform distribution of heat to the reradiator.

The principal function of the reradiator is to provide a large surface at a uniform high temperature, resulting in the conversion of a large percentage of the heat of combustion to radiant energy. In operation, the entire surface of the reradiator is heated to incandescence and may reach a temperature several hundred degrees above that of the primary radiant member.

The reradiator shown in FIGURE 7 is composed of the cylindrical sleeve 162 and cone-shaped cover 164 referred to above. These components are made of Inconel or other heat resistant material, are 0.018" thick, and are perforated with 331 uniformly spaced 0.033" diameters vent holes 172 per square inch of surface area. The reradiator may be of any other desired shape or construction, but that shown in FIGURE 7 is preferred as it attains a uniform high temperature, provides excellent combustion at a high input rate, converts a high percentage of the combustion heat to radiant energy, reaches operating temperature quickly, and has a low noise of extinction.

To be satisfactory, a reradiator must satisfy the following requirements: (at) its external surface area should be large in comparison to the radiant surface to provide high efficiency in converting heat of combustion to radiant energy; (b) the total area of the vent holes .172 should be large in comparison to the total area of openings 168 in the primary radiant member to reduce the back pressure within the combustion chamber and to vent the combustion gases quickly; (c) the size of the individual vent holes 172 should be small to protect the flame from disturbance by Wind; (d) the vent holes 172 should preferably (but not necessarily) be uniformly distributed over the entire area of the reradiator; (e) the primary radiator, the reradiator, and any bafiies used should be designed to distribute the heat uniformly over the reradiator so that it will attain a uniform temperature over its entire surface; (f) the volume of the combustion space Within the reradiator should be kept as small as possible to reduce noise of extinction to a minimum; and (g) the heat capacity (mass times specific heat) of the heated burner components should be minimized so that operating temperature may be quickly attained. All of these goals are attained to an unprecedented extent by the present invention.

For example, in the illustrated embodiment, the ratio of the area of the reradiator to the area of the primary radiant member is 7 to 1 as is the ratio of the total area of the vent openings 172 in the reradiator to the total area of the openings 168 in the primary radiant member. While both of these ratios may be reduced below this value, lower ratios tend to reduce both the maximum capacity and the efliciency of the unit, and a burner in which either ratio is less than 2 to 1 will be incapable of achieving the objects of this invention. The burners of the present invention will operate in the intended manner if these ratios are maintained in the range of 2: 1-10: 1. The preferred range is 5: 1-10: 1.

In addition to the individual vent holes 172 in the reradiator, six equally spaced diameter holes 174 are located near the end of reradiator sleeve 162 remote from radiant member 15%. Holes 174- permit the burner to be lighted from the outside of reradiator sleeve 162 as the flame will flash back through these holes and initiate combustion at 170. Vent holes 172 may be varied in size and shape or may be constituted by openings in a suitable Wire screen or other reticulated member. However, if holes 172 are too large or are not relatively uniformly distributed over the surface of the reradiator, the temperature of the reradiating surface will not be uniform, and Winds striking the heater may disturb the combustion.

Reradiator cover 164 is preferably a perforated cone, but may have some other shape and may be either perforate or imperforate.

Radiant heating unit 116 also includes a reflector 176 which, as shown in FIGURE 6, may be a bell-shaped member having an internal reflecting surface approximating the shape of a paraboloid and a bead 173 at its open end. The axis of symmetry of the reflector lies on the axis of symmetry of primary radiant member 153. The reflector is preferably formed of suitable aluminum alloy and may have either a matte or a polished interior surface. Shapes other than paraboloids may be used to form the emitted radiant energy into beams of various configurations. A number of suitable reflectors are disclosed in copending application No. 243,916.

To facilitate the assembly of gas inlet fitting 136, venturi 148, radiant unit 150, and reflector 176 to each other and to trunnions 113, to facilitate manufacture of heating unit 116, and to permit replacement of radiant unit 150, venturi 148 is formed of two longitudinally divided sheet metal halves 180, each of which has two flanges 182 (see FIGURES 6, 10 and 11). The flanges on one venturi half are spotwelded to the flanges on the other half at 134.

Venturi 143 is assembled to a U-shaped yoke 86 having an apertured base 188 through which gas inlet fitting 136 extends and to which the fitting is secured by locknut 140. Yoke 186 also has two arms 190 parallel to the axis of venturi 148. An angle 192 is spotwelded on the inside of each arm. These angles are fixed to venturi 148 by four'bolts 194, securing the venturi in proper relation to the orifice 144 in spud 142 (which is axially aligned with the venturi).

The'outlet end 196 of venturi 148 is welded around a central hole 198 in a square sheet steel plate 200. Plate 200 has flanges 202 turned toward the venturi inlet on all four sides and is perpendicular to the axis of the venturi. Hole 198 is the same size as the outlet of the venturi (see FIGURES 8 and 10).

Plate 200 is fastened by four bolts 204 to a round steel mounting plate 206 having a central hole 208 slightly 7 larger than the outlet of the venturi. A woven asbestos or otherweather and heat resistant gasket 210 is disposed betwen the two plates to prevent leakage of the gas-air mixture flowing from venturi 148 into distribution chamber 166. A spacer 212 (see FIGURE 14) having a central hole a locking plate 222 (see FIGURE 15) having a center hole 224 the same size as hole 214. Locking plate 222 is divided into two oppositely disposed ring quadrants 226 having the same outside diameter as spacer 212 and two oppositely disposed ring quadrants 228 having the same diameter as spacer ears 218. p

Locating plate 222 is welded on top of spacer 212 with the central holes 214 and 224 in the spacer and locking plate aligned and with one of the two radial edges 230 of the locking plate quadrants 228 aligned with each of the radial edges 220 on spacer 212. The corners 232 of the two remaining radial edges of locking plate quadrants 228 are bent away from plate 206 and spacer 212 to form tapered slots between locking plate quadrants 228 and spacer 212 as shown in FIGURE 7.

As shown in FIGURES 8 and 16, radiant unit base 'ring 152 is a flanged circular plate with a central hole 234 the same shape as the outside of plate 222 but slightly larger in all dimensions so that plate 222 can pass through hole 234, positioning radiant unit base ring 152 between plates 206 and 222. Radiant unit 150 may then be locked between plates 206 and 222 by rotating it in a clockwise direction (with reference to FIGURE 8). Bent up corners 232 guide ring 152 into the space between plates 206 and 222, and edges 220 on plate 206 act as stops, limiting the movement of ring 152 to a little less than 90 degrees. The difference in thickness between plate 206 and ring 152 is only a few thousandths of an inch so that member 150 will remain in position until removed byrotating it in the reverse or counterclockwise direction. a

' A flared. guide ring 236 (FIGURE 7) having a bottom flange 238 spot welded to plate 206 centers unit 150 as it is placed in position.

As best shown in attached to plate 200 by spot welding them to flanges 202 at diagonally opposite corners of the plate. Each bracket 240 is formed of two similar members fixed together in mirror image relationship by spot welding together their central rectangular webs 242. Triangular gussets 244, formed at an angle of 135 degrees to webs 242, are spot welded to flanges 202; and wings 246 on the sides of the webs oppositethe gussets' are turned outward 90 degrees to provide a flat surface at 45 degrees to flanges 202., Holes 248 are pierced through one wing on each bracket. As shown in FIGURE 11, both holes 248 are on the same side of a, diagonal through the corners of plate 200 to which brackets 240 are attached. These holes receive trunnions 118 as shown in FIGURE 6 and form bearings about which the burner maybe vertically tilted.

Nuts 250 are welded to wings 246 at points equidistant from holes 248. and in line with holes 252 in the wings.

Hand screws 254 with threaded stems 256 and shoulders 258 are screwed into the nuts and, when tightened, lock brackets 240 to swivel bracket 120. I

To' supply air to the burner while protecting it from the elements, three shields are arranged around venturi 148. One conical shield 260 (FIGURE 6) has a coneshaped portion 262, a flat bottom 264, and a cylindrical flange '266. Bottom portion 264 has a central hole 268 the same size as the hole in yoke 186. Gas inlet fitting 136 passes through these holes, and shield bottom 264 is clamped between the fitting and the yoke by-locknut FIGURE1 7, two brackets 240 are 140. Two curved shields, a lower perforated shield 270 and an upper unperforated shield 272, are spotwelded and extend axially from flange 266 of shield 260. The three shields, 260, 270 and 272.completelyencase venturi 148 except for two slots 274 between the curved shields which provide spaces through which webs 242 of brackets 240 extend.

Combustion air passes from the exterior of the shield assembly through perforations 27 6 in the'lower mrforated shield, through slots 2 74, and through the space 278 between the ends of shields 270 and 272 and reflector 176 into venturi 148. The unperforated upper shield 272 defiects rain water which might otherwise enter the venturi.

Referring still to FIGURE 6, reflector 176 is also asj sembled to mounting plate 206. Reflector 176 has-four equally spaced embossed areas .280 around the large central hole 282 through which radiant unit 150 extends.

Embossed areas 280 facilitate positioning the reflector on a plate 206. Each embossed area 280 has a central hole 284. Plate 206 has four segments 286 outside the perimeter of plate 200 which lie against the four embossed areas on the reflector. Holes 288 in the center of these segments (see FIGURE 8) are aligned with holes 284 when heater 116 is assembled. Nuts290 are welded to plate 206 on the side opposite. the reflector and in line with holes 288. Screws 292 (FIGURE 6) are threaded through holes 284 and holes 288 into nuts 290 to attach'reflector 176' to mounting plate 206.

Four A diameter holes 294 are formed in the top of reflector 176'near its rear end. These holes prevent heated air from becoming trapped when the burner is tilted downward as shown in FIGURE 1.

The assembly of components formed in the manner.

just described constitute heating unit 116 which is mounted on swivel bracket 120 which, as shown in FIGURES 1, 2 and 6, comprises a tube 296 with a yoke 298 welded to its upper end. Tube 296 is large enough to fit loosely on the upper end of post 122 and has a slot 300extending half way around its circumference. A handscrew 302 ex tends through slot 300 into a tapped hole 304 in the post.

Yoke 298 (see FIGURES 1, 2, and 6) is'a sheet steel 1 member and has a'base portion 306 which is welded'to tube 296, two opposed integral diagonal arm portions 308,

and two parallel portions 310 which are integral with the upper'ends of the arm portions and shaped to support heating unit trunnions 118 and handscrews 254. Trunnions 118 extend through holes 312 in'yoke arm portions 310. They are made from standard rivets with their heads welded to the, outside of arm portions 310 and extend into holes 248 in brackets 240. The yoke is sprung apart far enough to insert the trunnions into the holes 248 when heating unit 116 is assembled to swivel bracket 120. V

Formed in each yoke arm portion 310 is a curved slot 314 with its centerline spaced from the center of hole 312 a distance equal to the distance between the center of hole 248 and the center of nut 250. Slot 314'extends over an angle of 60 degrees (30 degrees up and 30 degrees down from a horizontal line through hole 312). The slot is slightly wider than the diameter of handscrew stern 256 which extends through the slot. 'Handscrew 254 has .3 shoulder 248, mentioned above, by which yoke arm-portions 310 and wings 246 of heater bracket 240 may be clamped together. When both handscrews are loosened, unit 116 can be tilted on trunnions 118 to direct the beam of infrared radiation upward, downward, or horizontally as the user desires.

Arms 310 are so shaped and trunnions 118 are so located that reflector 176 will clear the other parts of heating unit 116 in any position in which the unit may be located; and flexible hose 132 is attached as shown in FIGURE 2 to permit the unit to swing to the extreme end positions in any direction. In FIGURE 1, heating unit 116 is shown tilted down to full lines and in a horizontal position in broken lines.

A guard 316 is fastened over the open front of reflector 36 to prevent inadvertent contact with the incandescent radiant unit 150. As shown in FIGURES 12 and 13, guard 316 is made of three concentric wire rings 318, 320 and 322 connected by three equiangularly spaced wires 324, each in the form of a V having an angle of 60 degrees. The ends of wires 324 fit around reflector rim 178 at equally spaced angles.

The flow of gas to heating unit 116 is controlled by manipulation of the valve 126 in control casing 128. The manual valve 126 shown in FIGURE 1 may be replaced by any other suitable control unit; and the burner may be ignited manually or electrically by a spark from a high voltage circuit including the secondary winding of a transformer (see FIGURES l, 4 and 5) which may be housed in control casing 128.

Casing 128 has an inverted U-shaped body 326 with a flat top 328 and sides 330 welded at their edges to post 122. The edge of top 328 is curved to fit the periphery of the post. Inwardly extending, cover retaining flanges 332 are formed at the bottom of each side. A channel-sectioned, cover sealing rubber gasket 334 is fitted over the front open edge of body 326. This front opening is covered by a removable cover 336 which is flanged on all sides and fits around and against gasket 334. Bottom flange 338 of the cover casing fits inside body 326 and has a downturned portion 340 which hooks behind the flanges 332 on casing body 326. A spring catch 342, attached as by welding to the inside of cover 334, engages an angle 344 Welded to the inside of top 328, holding the cover in place, but allowing its ready removal to provide access to the valve.

In the following embodiments of our invention, certain components are identical to the corresponding components of the preferred embodiment of the invention described above. Insofar as these components are the same, they have, inv general, been identified by the same reference characters.

The modified reradiator sleeve 346 shown in FIGURES 18 and 19 has slots 348 lanced through the sleeve wall instead of the perforated holes 172 used in reradiator sleeve 162. Slots 352 may have a length 350 of A" and a maximum depth 353 of A The slots may be staggered in rows, the slots in each row being located at a center-to-center distance 354 of /2"; and the rows may be spaced apart a distance 356 of /8". In forming the slots, the metal is sheared outward from the reradiator sleeve, providing louvers 358 on the outside of sleeve 346 with their openings directed toward the venturi end of radiant unit 150.

The use of lanced louvers instead of perforated holes provides more radiant surface since the holes remove about 30% of the metal from the wall. The louvers also reduce the disturbing effect of the wind since they prevent a wind which might blow across reradiator 346 from passing directly through the openings.

The modified reradiator sleeve 360 shown in FIG- URES 20 and 21 is made of expanded metal. Expanded metal, which is a commercially available product, is produced by slitting sheet metal in a desired pattern and spreading the slits. One useful form of expanded metal, as shown in FIGURE 20, has diamond shaped openings 362 with a length 364 of and a width 366 of & the openings are staggered in rows spaced apart in the direction of the length of the openings a distance 368 of 4s". The rows are spaced apart a distance 370 of V As shown in FIGURE 21, the section through the expanded metal is like a series of shutters, so that the opening 366 measured parallel to the surface of the sheet is much smaller than the opening 372 between the slanting strips 374. Strips 374 are pitched so that the open ings on the outside are directed toward the venturi end of reradiator 360.

In the modified radiant unit 376 shown in FIGURES 22, 23, and 24, a sheet metal cross 378 is inserted in re radiator sleeve 162 between primary radiant cone 158 and reradiator cone 164. Cross 378 is made of three pieces, a flat plate 380 and two angles 382. The short legs 384 of angles 382 are spotwelded to plate 380 with the longer angle legs 386 perpendicular to plate 380 and extending on opposite sides thereof, as shown in FIG- URE 23.

Cross 378 divides the interior of radiant unit 376 into four quadrants and thereby prevents cross winds from blowing through openings 172 into the interior of radiant unit 376 and out openings 172 on the opposite side and disturbing combustion. Thus, the addition of cross 378 makes the unit more suited for operation in strong winds. In each arm of cross 378 there is a hole 388 which permits flame to flash from one quadrant to another to ensure ignition of the combustible gas-air mixture on the radiant face in each quadrant.

The modified radiant unit 390 shown in FIGURE 25 includes a base ring 392, a sleeve 394, a radiant support ring 396, a primary radiant member 398, a baffle 408, a reradiator sleeve 402, and a reradiator cover 404, all attached together by welding.

Primary radiant member 398 is a flat disc of Inconel wire screen. A circular disc made of 0.008" diameter Inconel wire spaced 40 Wires per inch will give good results when used with natural gas. Radiant support ring 396 has an angle-type section forming a cylindrical wall 406 which fits inside sleeve 394 and a flat annular wall 408 which is attached to the periphery of primary radiant member 398.

Baflle 400 is a flat disc of heat resistant material about %1" in diameter overlying the central portion of radiant member 398. Base ring 392 and sleeve 394 may be identical to the corresponding components 152 and 154 in the preferred embodiment. Reradiator sleeve 402 is made of wire screen which may be composed of 0.032" diameter Inconel wires spaced 12 Wires per inch. This spacing is great enough that, if the gas is lit on the outside of sleeve 402, the flame will flash through the screen, igniting the gas-air mixture at the surface of radiant disc 398.

In accordance with the present invention, disc 398 is constructed so that it will have a C number less than 0.0005, preventing the flame from flashing back through the disc, even though the disc is incandescent. Reradiator cover 404 is a hemispherical shell made from thin imperforate Inconel sheet and is heated to incandescence along with reradiator sleeve 482.

In the modified heating unit 410 shown in FIGURE 26, the radiant unit 412 is similar to radiant unit of the preferred embodiment, but has a sparkplug 414 attached to a bafiie 416 which replaces baflie 152 of radiant unit 150. Bafiie 416 has a centrally apertured flat top 418 and a hollow, internally threaded cylindrical body 420. A cylindrical porcelain insulator 422 fits within the cvlindrical body 420 of bafile 416 and projects through the hole 424 in the top of the bafiie into the combustion space. The opposite end of insulator 422 extends into venturi 426 which is identical to venturi 148 except that a hole 428 is cut in one side thereof. An externally threaded nut 438, screwed into the internal threads of baflle body 420, holds insulator 422 in position.

A wire electrode 432 extends longitudinally through the center of insulator 422. The part of the electrode within the combustion space is bent to form an approximately A spark gap 434 between the electrode and baffle 416 (which is grounded to complete the spark gas circuit).

The other end of electrode 432 contacts a spring conductor 436 which extends through an insulator 438, fas- 1 1 tened into hole 428 in venturi 426, to a conductor 439 which passes through bushing 440 in venturi shield 270.

Because of this construction, the electrical connections do not interfere with the detachment of the radiant unit ,inthe manner previously described; and no wires need be nected by a capillary tube 446 to a flexible wafer 448.

Wafer 448 has a movable diaphragm which depresses a lever 450 when the liquid in bulb 444 expands, opening a set of switch contacts 452 in the illustrated solenoid actuating electrical circuit. This circuit also includes a switch S454, which may be manually or thermostatically operated, a thermal relay 456, a resistor R458, a'solenoid relay 460, and an ignitor transformer T462.

In this circuit, current is supplied to solenoid 473 through lines L464 and L466. When switch S454 is closed, a circuit is established from line L464 through thermal relay resistor R468, solenoid coil 460, switch contacts 452, lever 450, and lever pivot 470 to line L466. Simul taneously, a parallel circuit is established from line L464 through a bimetallic strip 472, resistor R458, and the solenoid coil 413 of valve 442 to line L466, but resistor R458 is of sufliciently high resistance that valve 442 will 7 not open at this point.

Current through relay coil 460 causes the relay contacts 474 to close, establishing two branch circuits. One is through transformer primary winding 476 to line L466 'which induces current to flow in the circuit through transcausing a spark across spark gap 434.

The other branch circuit shorts out resistor R458, causing an increased current flow through and energizing solenoid coil 473, which open fuel valve 442. Gas then flows through supply pipe 124 and inlet 136 into venturi 426 where it is mixed with the combustion air. From venturi 426, the gas-air mixture flows through the perforations in radiant member 398 and is ignited by the spark across gap 434.

Heat from the combustion of the gas-air mixture causes the fluid in bulb 444 to expand as the bulb is located close to radiant member 412. Expansion of the fluid causes wafer 448 to bulge, depressing lever 450 against the force of a spring 482 and opening cont-acts 452. This deenergizes relay 460 and causes normally open contacts '474 to reopen, which stops the spark. Current continues to flow-through bimetal strip 472, resistor R458, andvalve coil 473. This current is suflicient to hold valve 444 open, but not open the valve if it is closed.

1 of like capacity, making the structure particularly suit-.

able for use with vents extending directly through the If the burner fails to light within a short time, or if the flame is extinguished, bulb 444 will not be heated, contacts 452 will remain closed, and an increased magnitude current will flow through resistor R468, causing it to heat bimctal strip 472 which will open contacts 486, cutting off current to coil 473 and closing valve 444. Switch S454 must then be opened to restore the components to their original condition. The burner can then be relighted as soon as bimetallic'strip 472 cools.

Combustion can be stopped by opening switch S454 which immediately cuts off current to coil 473, causing valve 444 to close and deenergizing transformer'462.

FIGURE 27 shows a typical application of the heating unit of the present invention for supplying heat to a heat exchanger, in this case a hot air furnace 488 including a combustion chamber 490, a flue 492, an outer jacket 494, a blower 496, and a combustion air supply duct 498 connected to a burner compartment 508.

Radiant unit 150, in this application, is attached to the bottom wall 502 of combustion chamber 490 and extends upwardly into the combustion chamber along its central axis. Unit is attached in the same manner as previously described in conjunction with the assembly of the unit to mounting plate 206 in the preferred embodiment. Venturi 148 is welded to a hole in combustion chamber wall 502 in axial alignment with unit 150. Gas is supplied to venturi 148 through spud 142, which is connected in the usual manner to a gas supply and control system (not shown). A lighting door (not shown) in the wall of combustion chamber 490 provides access to the interior for lighting or servicing the burner. All combustion air enters through venturi 148. Heat is transmitted by radiation and convection from radiant 150 to the walls of a combustion chamber 490, warming the air circulated by blower 496.

radiation upward. Because there is no air flowing through' thecombustion chamber other than. that passing through the burner, air and flue gas heat losses are extremely low, producing an unusually high efliciency. In addition, heat transfer by radiation from the radiant member 150 is very efficient.

Venturi 150 and spud 142 with its associated gas conduit may be replaced with a conduit supplying premixed gas and air, if desired.

Because of the low excess air, flue 492 may be smaller in diameter than is usual for convention gas appliances wall. The flue may incorporate a conventional draft regulator or diverter. V 7

This type of application of the burners of this invention has similar utility in connection with other heat transfer applications such as heating liquids or drying materials.

The invention may be embodied in'other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative'and not-restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters 7 Patent is: a

1. An infrared generator of the combustion type comprising:

7 (a) an apertured primary radiant member of thin, heat resistant metal plate operating at'incandesc'ent temperatures;

(b) means for forcing a mixture of-a combustible gas and all of the air required for'its complete combustion from one side of said primary radiant member through the apertures therein to a combustion zone immediately adjacent the exterior surface of said primary radiant member; and i (c) an apertured reradiating member of thinpheat resistant metal plate similar to that from which the primary radiant is fabricated operating at lIlCBJJdCS cent temperatures and surrounding said radiant member beyond the combustion zone thereadjacent,

whereby said combustion zone is confined-within said primary and reradiating members;

(d) the primary radiant member being with the small end thereof extending into the radiant member; i

(e) the apertures in the primary radiant member being sufliciently small to prevent flashback from the com bustion zone through said member to the combustible a truncated cone 13 ten times as great as the aggregate area of the apertures in the primary radiant member.

2. The infrared generator as defined in claim 1, wherein the aggregate area of the apertures in the reradiating member is between seven and ten times as great as the aggregate area of the apertures in the primary radiant member.

3. The infrared generator as defined in claim 1, wherein the apertures in the reradiating member are circular perforations.

4. The infrared generator as defined in claim 1, including a reflector surrounding said reradiator member.

5. The infrared generator as defined in claim 1, wherein the reradiating member is cylindrical and has one end near an end of the primary radiant member, said infrared generator further including a reradiating cover member near the other end of the reradiating member.

6. The infrared generator as defined in claim 1, wherein the apertures in the primary radiant member are circular perforations.

7. The infrared generator as defined in claim 1, wherein said combustible mixture forcing means includes a venturi having its outlet communicating with said one side of the primary radiant member and further including a shielding assembly surrounding the venturi to protect the infrared generator from the edects of wind and inclement weather, comprisin (a) an upper imperforate shield and a lower perforate shield forming a cylinder around the venturi; and

(b) a third shield fixed to the upper and lower shields and extending around the venturi inlet.

8. The infrared generator as defined in claim 1, further including:

(a) a support;

(b) swivel means mounting the infrared generator on said support and permitting rotational movement of the generator relative to the support in two mutually perpendicular planes; and

(c) a flexible gas supply line fixed at opposite ends to the generator and the support.

9. The infrared generator as defined in claim 1, wherein the apertures in said reradiating member are the gaps between generally semiconical louvers punched from the reradiating member and the resulting holes in said mem- 'ber.

10. The infrared generator as defined in claim 1, wherein the reradiating member is formed from heat resistant expanded metal and the apertures in said reradiating member are the openings in said metal.

11. An infrared generator of the combustion type, comprising:

(a) an apertured primary radiant member of thin, heat resistant metal plate;

(b) means for forcing a mixture of a combustible gas and all of the air required for its complete combustion into the interior of said member and through the apertures therein to a combustion zone immediately adjacent the exterior surface of said primary radiant member, said last-named means comprising a venturi having its outlet in communication with the interior of the primary radiant member and its inlet open to atmosphere and an orifice member at the inlet end of said venturi adapted to effect a high velocity flow of fuel into said venturi to induce a flow of combustion air thereinto;

(c) an apertured reradiating member of thin, heat resistant metal plate having an exterior surface with at least twice the area of the exterior surface of the primary radiant member surrounding said radiant member beyond the combustion zone, the aggregate area of the apertures in the reradiating member being at least twice the aggregate area of the apertures in the primary radiant member and less than one order of magnitude greater than the aggregate area of the apertures in the primary radiant member;

(d) an electrode insulated from the primary radiant member and extending therethrough to the interior of the reradiating member, the end of the electrode being spaced from the primary radiant member to form a spark gap therebetween;

(e) a spring contact fixed to the combustible mixture supply means and extending into abutting engagement with the electrode to permit removal of the radiant member without disconnecting the electrode; and

(f) means effective upon ignition failure or flame extinguishment to interrupt the flow of fuel into said venturi.

12. An infrared generator of the combustion type comprising:

(a) an apertured primary radiant member of thin, heat resistant metal plate operating at incandescent temperature,

(b) means for forcing a mixture of a combustible gas and all of the air required for its complete combustion from one side of said primary radiant member through the apertures therein to a combustion zone immediately adjacent the exterior surface of said primary radiant member; and

(c) an apertured reradiating member of thin, heat resistant metal plate similar to that from which the primary radiant is fabricated operating at incandescent temperatures and surrounding said radiant member beyond the combustion zone thereadjacent, whereby said combustion zone is confined within said primary and reradiating members, said reradiating member being cylindrical and having one end near an end of the primary radiant member;

((1) a reradiating cover member near the other end of the reradiating member; and

(e) baffiing inside the reradiating member extending between the primary radiant member and the reradiating cover member and dividing the space therebetween into a plurality of substantially mutually isolated areas;

(f) the apertures in the primary radiant member being sufficiently small to prevent flashback from the combustion zone through said member to the combustible mixture on said one side thereof with said member at a temperature above the ignition temperature of the combustible gas-air mixture; and

(g) the aggregate area of the apertures in the reradiating member being at least twice and not more than ten times as great as the aggregate area of the apertures in the primary radiant member.

13. The infrared generator as defined in claim 12, wherein the reradiating cover member is an apertured cone with the apex of the cone inside the reradiating member.

14. The infrared generator as defined in claim 12, wherein the reradiating cover member is apertured, has a substantially hemispherical configuration, and is disposed substantially wholly within the reradiating member.

References Cited UNITED STATES PATENTS (Other references on following page) 

1. AN INFRARED GENERATOR OF THE COMBUSTION TYPE COMPRISING: (A) AN APERTURED PRIMARY RADIANT MEMBER OF THIN, HEAT RESISTANT METAL PLATE OPERATING AT INCANDESCENT TEMPERATURES; (B) MEANS FOR FORCING A MIXTURE OF COMBUSTIBLE GAS AND ALL OF THE AIR REQUIRED FOR ITS COMPLETE COMBUSTION FROM ONE SIDE OF SAID PRIMARY RADIANT MEMBER THROUGH THE APERTURES THEREIN TO A COMBUSTION ZONE IMMEDIATELY ADJACENT THE EXTERIOR SURFACE OF SAID PRIMARY RADIANT MEMBER; AND (C) AN APERTURED RERADIATING MEMBER OF THIN, HEAT RESISTANT METAL PLATE SIMILAR TO THAT FROM WHICH THE PRIMARY RADIANT IS FABRICATED OPERATING AT INCANDESCENT TEMPERATURES AND SURROUNDING SAID RADIANT MEMBER BEYOND THE COMBUSTION ZONE THEREADJACENT, WHEREBY SAID COMBUSTION ZONE IS CONFINED WITHIN SAID PRIMARY AND RERADIATING MEMBERS; (D) THE PRIMARY RADIANT MEMBER BEING A TRUNCATED CONE WITH THE SMALL END THEREOF EXTENDING INTO THE RADIANT MEMBER; (E) THE APERTURES IN THE PRIMARY RADIANT MEMBER BEING SUFFICIENTLY SMALL TO PREVENT FLASHBACK FROM THE COMBUSTION ZONE THROUGH SAID MEMBER TO THE COMBUSTIBLE MIXTURE ON SAID ONE SIDE THEREOF WITH SAID MEMBER AT A TEMPERATURE ABOVE THE IGNITION TEMPERATURE OF THE COMBUSTIBLE GAS-AIR MIXTURE; AND (F) THE AGGREGATE AREA OF THE APERTURES IN THE RERADIATING MEMBER BEING AT LEAST TWICE AND NOT MORE THAN TEN TIMES AS GREAT AS THE AGGREGATE AREA OF THE APERTURES IN THE PRIMARY RADIANT MEMBER. 